Electrostatically clamped edge ring

ABSTRACT

An edge ring for use in a plasma processing chamber with a chuck is provided. An edge ring body has a first surface to be placed over and facing the chuck, wherein the first surface forms a ring around an aperture. A first elastomer ring is integrated to the first surface and extending around the aperture.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No. 15/343,010filed on Nov. 3, 2016, entitled “ELECTROSTATICALLY CLAMPED EDGE RING”,the entire contents of which are incorporated herein by referencethereto.

BACKGROUND

The disclosure relates to a method and apparatus for plasma processing asubstrate. More specifically, the disclosure relates to a method andapparatus for clamping an edge ring in a plasma processing chamber.

In plasma processing, a plasma processing chamber with an edge ring maybe used to provide improved process control.

SUMMARY

To achieve the foregoing and in accordance with the purpose of thepresent disclosure, a method for electrostatically clamping an edge ringin a plasma processing chamber with an electrostatic ring clamp with atleast one ring backside temperature channel for providing a flow of gasto the edge ring to regulate the temperature is provided. A vacuum isprovided to the at least one ring backside temperature channel. Pressurein the at least one ring backside temperature channel is measured. Anelectrostatic ring clamping voltage is provided when the pressure in theat least one ring backside temperature channel reaches a thresholdmaximum pressure. The vacuum to the at least one ring backsidetemperature channel is discontinued. Pressure in the at least one ringbackside temperature channel is measured. If pressure in the at leastone ring backside temperature channel rises faster than a thresholdrate, then sealing failure is indicated. If pressure in the at least onering backside temperature channel does not rise faster than thethreshold rate, a plasma process is continued, using the at least onering backside temperature channel to regulate a temperature of the edgering.

In another manifestation, an edge ring for use in a plasma processingchamber with a chuck is provided. An edge ring body has a first surfaceto be placed over and facing the chuck, wherein the first surface formsa ring around an aperture. A first elastomer ring is integrated to thefirst surface and extending around the aperture.

These and other features of the present invention will be described inmore details below in the detailed description of the invention and inconjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a schematic cross-sectional view of a plasma processingchamber with an embodiment.

FIG. 2 is a schematic view of a computer system that may be used inpracticing an embodiment.

FIG. 3 is an enlarged view of the etch ring and electrostatic ringchuck, shown in FIG. 1.

FIG. 4 is a bottom view of an edge ring of an embodiment.

FIG. 5 is a flow chart of an embodiment.

FIG. 6 is an enlarged view of part of the ESC system in anotherembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference toa few preferred embodiments thereof as illustrated in the accompanyingdrawings. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art, thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known process steps and/orstructures have not been described in detail in order to notunnecessarily obscure the present invention.

FIG. 1 is a schematic view of a plasma processing chamber that may beused in an embodiment. In one or more embodiments, the plasma processingsystem 100 comprises a gas distribution plate 106 providing a gas inletand an electrostatic chuck system (ESC system) 108 comprising a ceramicplate 112 and a base plate 114, within a processing chamber 149,enclosed by a chamber wall 150. Within the processing chamber 149, asubstrate 104 is positioned on top of the ESC system 108. The ESC system108 may provide a bias from the ESC source 148. A gas source 110 isconnected to the plasma processing chamber 149 through the distributionplate 106. An ESC temperature controller 151 is connected to the ESCsystem 108, and provides temperature control of the ESC system 108. Avacuum source 160 is connected to the ESC system 108. An RF source 130provides RF power to ESC system 108 and an upper electrode, which inthis embodiment is the gas distribution plate 106. In a preferredembodiment, 2 MHz, 60 MHz, and optionally, 27 MHz power sources make upthe RF source 130. In this embodiment, one generator is provided foreach frequency. In other embodiments, the generators may be in separateRF sources, or separate RF generators may be connected to differentelectrodes. For example, the upper electrode may have inner and outerelectrodes connected to different RF sources. Other arrangements of RFsources and electrodes may be used in other embodiments, such as inanother embodiment the upper electrodes may be grounded A controller 135is controllably connected to the RF source 130, the ESC source 148, anexhaust pump 120, and the etch gas source 110. An edge ring 116 issupported by the ESC system 108 at the outer edge of the substrate 104.An example of such a plasma processing chamber is the Exelan Flex™ etchsystem manufactured by Lam Research Corporation of Fremont, Calif. Theprocess chamber can be a CCP (capacitive coupled plasma) reactor or anICP (inductive coupled plasma) reactor or may be another type of poweredplasma in various embodiments.

FIG. 2 is a high level block diagram showing a computer system 200,which is suitable for implementing a controller 135 used in embodimentsof the present invention. The computer system may have many physicalforms ranging from an integrated circuit, a printed circuit board, and asmall handheld device, up to a huge super computer. The computer system200 includes one or more processors 202, and further can include anelectronic display device 204 (for displaying graphics, text, and otherdata), a main memory 206 (e.g., random access memory (RAM)), storagedevice 208 (e.g., hard disk drive), removable storage device 210 (e.g.,optical disk drive), user interface devices 212 (e.g., keyboards, touchscreens, keypads, mice or other pointing devices, etc.), and acommunication interface 214 (e.g., wireless network interface). Thecommunication interface 214 allows software and data to be transferredbetween the computer system 200 and external devices via a link. Thesystem may also include a communications infrastructure 216 (e.g., acommunications bus, cross-over bar, or network) to which theaforementioned devices/modules are connected.

Information transferred via communications interface 214 may be in theform of signals such as electronic, electromagnetic, optical, or othersignals capable of being received by communications interface 214, via acommunication link that carries signals and may be implemented usingwire or cable, fiber optics, a phone line, a cellular phone link, aradio frequency link, and/or other communication channels. With such acommunications interface, it is contemplated that the one or moreprocessors 202 might receive information from a network, or might outputinformation to the network in the course of performing theabove-described method steps. Furthermore, method embodiments of thepresent invention may execute solely upon the processors or may executeover a network such as the Internet, in conjunction with remoteprocessors that share a portion of the processing.

The term “non-transient computer readable medium” is used generally torefer to media such as main memory, secondary memory, removable storage,and storage devices, such as hard disks, flash memory, disk drivememory, CD-ROM, and other forms of persistent memory, and shall not beconstrued to cover transitory subject matter, such as carrier waves orsignals. Examples of computer code include machine code, such as oneproduced by a compiler, and files containing higher level code that areexecuted by a computer using an interpreter. Computer readable media mayalso be computer code transmitted by a computer data signal embodied ina carrier wave and representing a sequence of instructions that areexecutable by a processor.

FIG. 3 is an enlarged view of part of the ESC system 108 and substrate104. The ESC system 108 comprises a ceramic plate 112 and a base plate114. An elastomer bond 304 holds the ceramic plate 112 to the base plate114. In a raised central portion 306 of the ceramic plate 112 aresubstrate clamping electrodes 308, which are used to apply a voltage toelectrostatically chuck the substrate 104. At least one substratechucking clamping electrode lead 309 is connected between the substrateclamping electrodes 308 and the ESC source 148, shown in FIG. 1. In alower peripheral portion 310 of the ceramic plate are edge ring clampingelectrodes 312, which are used to apply a voltage to electrostaticallychuck the edge ring 116. At least one edge ring clamping electrode lead314 is connected between the edge ring clamping electrodes 312 and theESC source 148, shown in FIG. 1. In one embodiment, the ESC source 148may be a plurality of voltage sources. In another embodiment, the ESCsource 148 may be a single voltage source with a plurality of switchesto independently apply different voltages to the substrate clampingelectrodes 308 and the edge ring clamping electrodes 312. A portion ofthe lower peripheral portion 310 may be recessed to form a gap formed bya cooling groove 350 between the lower peripheral portion 310 and theedge ring 116. The cooling groove 350 provides a region, which allowsthe coolant to flow near the backside of the edge ring 116, andfacilitate creating a seal for the coolant.

In the raised central portion 306 is a plurality of substrate backsidetemperature channels 320, which are connected through a fluid connection324 to the ESC temperature controller 151, shown in FIG. 1. In the lowerperipheral portion 310 are a plurality of ring backside temperaturechannels 328, which are connected through a fluid connection 332 to theESC temperature controller 151, shown in FIG. 1. A first sealing groove336 in the upper surface of the lower peripheral portion 310 makes aring around the raised central portion 306. A second sealing groove 340in the upper surface of the lower peripheral portion 310 makes a ringaround and is concentric with the first sealing groove 336.

The edge ring 116 comprises an edge ring body 394 and a first elastomerring 344 integrated to the edge ring body 394 and a second elastomerring 348 integrated to the edge ring body 394. FIG. 4 is a bottom viewof the edge ring 116. The bottom of the edge ring 116 forms a firstsurface 404, which is also shown in FIG. 3. The edge ring 116 has anouter diameter 408 and an inner diameter 412. In this example, the outerdiameter is 400 mm and the inner diameter is 290 mm. Within the innerdiameter is a central aperture of the edge ring 116. In this example,the edge ring 116 is formed from silicon, so that the edge ring 116,including the first surface 404, is conductive. In this example, thefirst elastomer ring 344, and the second elastomer ring 348, and theedge ring 116 are all concentric, as shown. The hole in the center ofthe edge ring 116 forms a central aperture, as shown.

The edge ring clamping electrodes 312 form an electrostatic ring chuck.The substrate clamping electrodes 308 form an electrostatic wafer chuck.If the entire edge ring 116 or first surface 404 is not conductive, thenthe edge ring 116 would need to have conductive portions. As shown inFIG. 3, when the edge ring 116 is mounted on the electrostatic ringchuck, so that conductive portions of the edge ring 116 are over theedge ring clamping electrodes 312 and the raised central portion 306passes through the central aperture, the first elastomer ring 344 isplaced in the first sealing groove 336 and the second elastomer ring 348is placed in the second sealing groove 340.

In this example, the first sealing groove 336 and the second sealinggroove 340 have a depth of 0.5 mm. The first elastomer ring 344 and thesecond elastomer ring 348 have a height of 0.5 mm after clamping.

FIG. 5 is a high level flow chart of a process for chucking the edgering 116. The edge ring 116 is placed on the electrostatic ring chuck(step 504). The edge ring 116 may be placed on the electrostatic ringchuck, as shown in FIG. 1 and FIG. 3. The electrostatic ring chuck isformed by the edge ring clamping electrodes 312. The lower peripheralportion 310 of the ceramic plate 112, the first sealing groove 336 inthe upper surface of the lower peripheral portion 310, the secondsealing groove 340 in the upper surface of the lower peripheral portion310, the cooling groove 350, and the plurality of ring backsidetemperature channels 328 may further make up the electrostatic ringchuck. A vacuum is provided to the plurality of ring backsidetemperature channels 328 by connecting the fluid connection 332 tovacuum source 160 (step 508). The vacuum source 160 provides a vacuum,which causes the edge ring 116 to move towards the upper surface of thelower peripheral portion 310, which causes the first elastomer ring 344and the second elastomer ring 348 to be compressed within the firstsealing groove 336 and the second sealing groove 340, respectively.Preferably, the chamber pressure is atmospheric pressure, so that thepressure on top of the edge ring 116 is atmospheric pressure. Theapplied vacuum causes mechanical movement of the edge ring 116 tofacilitate electrostatic clamping of the edge ring 116 and allows fortesting of the seal. The pressure in the backside temperature channelsis measured. When the pressure is lowered to a threshold pressure, aring clamping voltage is applied (step 512). The pressure thresholdindicates that the edge ring 116 has been forced to a thresholddistance, which will allow the edge ring clamping electrodes 312 toclamp the edge ring 116. The application of the vacuum is thendiscontinued (step 516). Pressure in the backside temperature channels328 is measured (step 520). If the measured pressure increase is largerthan a threshold rate, it indicates that the seal has failed (step 524).Then the seal must be re-created (step 528). This may be done byre-seating the edge ring. This may require replacing the edge ring 116so that the first elastomer ring 344 and the second elastomer ring 348are replaced. If the measured pressure increase is smaller than thethreshold rate, it indicates that the seal is sufficient. The backsidetemperature channels 328 are then used for temperature control of theedge ring 116 (step 532). The edge ring clamping electrodes continuouslyclamp the edge ring during the placement of a substrate over thesubstrate clamping electrodes of the ESC system, and during the clampingof the substrate, the processing of the substrate, the declamping of thesubstrate, and the removal of the substrate. Therefore, the ringclamping electrodes and the substrate clamping electrodes are operatedindependently, allowing the ring clamping electrodes to continuouslyclamp, while the substrate clamping electrodes are used to clamp andsubsequently declamp the substrate.

This embodiment provides an edge ring seal, which allows for temperaturecontrol of the edge ring. Allowing temperature control of the edge ringprovides greater control during plasma processing, which improves theplasma processing.

This embodiment provides various advantages over a configuration thatuses O-rings. In order to use an O-ring for the similar purposes, theO-ring would need to be thin with a large diameter and be made of a softmaterial. The placement of such an O-ring to create the desired sealwill require a highly skilled technician, due to the fragileness of theO-ring and the various requirements to create the seal, such aspreventing pinching or bunching of the O-ring. This embodiment allows aless skilled technician to simply and easily place the edge ring on theelectrostatic ring chuck.

In other embodiments, the ceramic plate may be in two parts, with theraised central portion 306 being separate from the lower peripheralportion 310. The entire edge ring may be made of a conductive material,such as silicon. In other embodiments, the edge ring is a dielectricmaterial with conductive parts, which would be placed over the ringclamping electrodes when the edge ring is placed on the electrostaticring chuck. The conductive parts facilitate electrostatic clamping.Preferably, the edge ring is at least one of silicon, silicon carbide,or quartz.

In various embodiments, the height of each elastomer ring is greaterthan the depth of the groove in which the elastomer ring is placed. Thiscauses the elastomer ring to be compressed when creating the seal, whichhelps to establish the seal. In various embodiments, the elastomer mayhave different cross-sections. Preferably, the cross-section of theelastomer ring is at least one of rectangular, square, triangular,trapezoidal, or semicircular. More preferably, the bottom of thecross-section of the elastomer ring is narrower than the top of theelastomer ring, which is integrated with the rest of the edge ring. Mostpreferably, the elastomer ring is trapezoidal, as shown in FIG. 3.Preferably, the elastomer ring has a height between 0.25 mm to 2 mm.Preferably, the height of the elastomer ring is between 10 to 50 micronsgreater than the depth of the groove. Preferably, the tolerance of theheight of the elastomer ring is 50 microns or better. More preferably,the tolerance of the height elastomer ring is 12-13 microns. Preferably,the outer diameter of the edge ring is between 200 mm to 450 mm. Morepreferably, the outer diameter of the edge ring is between 300 mm to 400mm. Preferably, the edge ring, the first elastomer ring, and the secondelastomer ring are concentric. Preferably, the first elastomer ring iswithin 10 mm of the inner edge of the edge ring and the second elastomerring is within 30 mm of the outer edge of the edge ring.

In chucking a wafer, an elastomer ring is not needed, since a wafer willbend to help create a seal. Since edge rings are much thicker than awafer, the edge ring does not sufficiently bend to create a seal withoutelastomer rings. In some embodiments, the elastomer ring may be formedby applying a wet or liquid elastomer on the edge ring, and then dryingor solidifying and curing the elastomer on the edge ring. In variousembodiments, the elastomer ring is made of a soft elastomer that willnot outgas beyond a specific limit, such as silicone. Preferably, anelastomer ring comprises silicone with a ring diameter of at least 200mm and a height between 0.25 mm to 2 mm. Preferably, the thickness of across-section of the elastomer is less than 3 mm. Preferably, anelastomer ring comprises silicone with a diameter of at least 200 mm anda height between 0.25 mm to 1.5 mm. The grooves in the surface of theceramic plate allow the surface of the edge ring to be placed close tothe electrostatic ring clamps to allow clamping. The height of theelastomer ring and depth of the groove with some compression of theelastomer ring provides a gas seal around the circumferences of theelastomer rings and while compensating for 20 microns of nonflatness ofthe edge ring, which requires an additional 20 microns of elastomercompression (elastomer compression is height of elastomer seal minus thegroove depth). An optional feature in the surface of the ceramic plateprovides a 10 micron gap between the surface of the ceramic plate andthe edge ring. The gap 350 can range from 0 microns to 20 microns.

In an embodiment, the height of the elastomer is equal to the depth ofthe groove plus the tolerance of the groove depth plus the tolerance ofthe elastomer seal height (all assuming symmetric tolerances) plus theflatness of the edge ring. So if the groove depth is 0.5 mm±25 um, theelastomer seal can be controlled to within ±15 um of target height, andthe flatness of the ring is 20 um, then the elastomer seal target heightshould be 0.5 mm+25 um+15 um+20 um=0.56 mm. This ensures that when theelastomer is at its smallest height, and groove is at its largest depth,and flatness at its worst, the seal will still make contact with thering surface at the bottom of the groove. Since having all items atworst case simultaneously is unlikely, we sometime use RSS addition, inwhich case elastomer seal target height should be 0.5 mm+square root (25um²+15 um²+20 um²)=0.535 mm.

In an embodiment, the edge ring has a thickness of at least 1 mm inorder to tolerate wear during plasma processing and to provideflexibility in height. In some embodiments, the edge ring has an uppersurface that is above the upper surface of the wafer to provide sheathcontrol.

Preferably, the backside temperature control channels are heliumchannels that carry helium gas coolant. The coolant is used to cool boththe substrate and the edge rings. Such an embodiment allows fortemperature control of both the substrate and edge ring. In addition,the embodiment allows for separate temperature control of the substrateand edge ring. In other embodiments, other gases or liquids may be usedas a coolant, such as argon, air, nitrogen, or a liquid with a very lowvapor pressure.

FIG. 6 is an enlarged view of part of the ESC system 108 and substrate104 in another embodiment. The ESC system 108 comprises a ceramic plate112 and a base plate 114. An elastomer bond 604 holds the ceramic plate112 to the base plate 114. In this embodiment, the ceramic plate 112comprises a central substrate support section 606 and a peripheral ringshape edge ring support section 610. In the edge ring support section610 of the ceramic plate 112 is a circular cooling groove 650, whichsurrounds the substrate support section 606 and central aperture of theedge ring support section 610. Under the bottom of the cooling groove650 are edge ring clamping electrodes 612, which are used to apply avoltage to electrostatically chuck the edge ring 116. At least one edgering clamping electrode lead 614 is connected between the edge ringclamping electrodes 612 and the ESC source 148, shown in FIG. 1. Thecooling groove 650 causes a gap to be between the edge ring supportsection 610 and the edge ring 116, when the edge ring 116 is placed onthe edge ring support section 610.

In the edge ring support section 610 are a plurality of ring backsidetemperature channels 628, which are connected through a fluid connection632 to the ESC temperature controller 151, shown in FIG. 1 and to thecooling groove 650. The edge ring 116 has an elastomer ring 644integrated to the edge ring 116. In this example, the elastomer ring 644is in the shape of a sheet forming a ring. Preferably, the sheet is nomore than 25 microns thick and a width that is greater than the width ofthe cooling groove 650.

The edge ring clamping electrodes 612, the cooling groove 650, and theedge ring support section 610 form an electrostatic ring chuck. As shownin FIG. 6, when the edge ring 116 is mounted on the electrostatic ringchuck, so that conductive portions of the edge ring 116 are over theedge ring clamping electrodes 612 and the central substrate supportsection 606 passes through the central aperture, the elastomer ring 644and the elastomer ring 644 extends across the cooling groove 650, asshown.

While this invention has been described in terms of several preferredembodiments, there are alterations, modifications, permutations, andvarious substitute equivalents, which fall within the scope of thisinvention. It should also be noted that there are many alternative waysof implementing the methods and apparatuses of the present invention. Itis therefore intended that the following appended claims be interpretedas including all such alterations, modifications, permutations, andvarious substitute equivalents as fall within the true spirit and scopeof the present invention.

What is claimed is:
 1. An edge ring for use in a plasma processingchamber with a chuck, comprising: an edge ring body with a first surfaceto be placed over and facing the chuck, wherein the first surface formsa ring around an aperture; and a first elastomer ring integrated to thefirst surface and extending around the aperture.
 2. The edge ring, asrecited in claim 1, further comprising a second elastomeric ringintegrated to the first surface and extending around the aperture. 3.The edge ring, as recited in claim 2, wherein the first elastomeric ringis concentric with the second elastomeric ring.
 4. The edge ring, asrecited in claim 2, wherein the edge ring body, first elastomer ring andsecond elastomer ring are all concentric.
 5. The edge ring, as recitedin claim 4, wherein the edge ring body has an outer diameter between 200mm to 400 mm.
 6. The edge ring, as recited in claim 5, wherein the firstsurface of the edge ring body has an inner edge and an outer edge,wherein the first elastomer ring is within a distance of 10 mm from theinner edge of the first surface and the second elastomer ring is withina distance of 30 mm from the outer edge of the first surface.
 7. Theedge ring, as recited in claim 1, wherein the first elastomer ring has aheight of between 0.25 mm and 2 mm.
 8. The edge ring, as recited inclaim 1, wherein a tolerance of the height of the first elastomer ringis 50 microns or better.
 9. The edge ring, as recited in claim 1,wherein the first elastomer ring is formed from a material comprisingsilicone.
 10. The edge ring, as recited in claim 1, wherein the firstelastomer ring has a cross-section in the shape of a trapezoid, square,rectangle, triangle, or semicircle.
 11. The edge ring, as recited inclaim 1, wherein the edge ring body has an outer diameter between 200 mmto 400 mm.
 12. The edge ring, as recited in claim 1, wherein the edgering body comprises at least one of silicon, silicon carbide, or quartz.13. The edge ring, as recited in claim 1, wherein the first elastomerring is applied to the first surface as a liquid elastomer.